Quantity of Seeds

The easiest way to manipulate particle size and particle size distribution is by seeding. Often this power of seeding is underestimated or neglected. Instead, just a few seeds are added to the supersaturated solution in order to somehow start the crystallization process. By this homeopathic seeding, a lot of potential control over the crystallization process is given out of hand. 

The particle size obtained by a seeded crystallization is determined by the amount of seeds and their particle size. The final size can be estimated by assuming that (1) the number of particles introduced as seed, Ttseed. is constant and (2) all seed particles grow at the same rate. If the seed particle size is narrowly distributed around ds, the product particle size is given by Equation 10.3  

The assumption of a constant seed particle number heavily depends on the seed particle size the smaller the seed particles, the more they are prone to agglomeration, and the introduction and the proceeding of the crystallization the higher the power input, the more the particles are prone to breakage and secondary nudeation. 

In general, for a 10-fold increase in particle size via seeding, 0.1% of seed is needed. 

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Add selected quantity of seed crystals having specified CSD. ... 

There is evidence for Cannabis use as early as 5,000 B.C. in Central Europe and there are probable references to it in the earliest writings of China and Egypt. The frozen tombs of the inhabitants of Siberia in about 500 B.C. have yielded quantities of seeds along with a variety of devices for burning them. A very hot, dry climate appears necessary for producing grass with high psychedelic activity, which may account for the failure to use Cannabis as an intoxicant in Northwestern Europe. ... 

All experiments up to this time employed only minute quantities of seed crystals. In investigating the variables affecting the growth of the dextrose crystals, Newkirk found that the operation could be controlled by using much greater proportions of seed crystals than had hitherto been employed.8 The excessive formation of crystal nuclei too small and numerous to be able to grow to satisfactory size could be avoided by this means. The operation was most economically carried out by leaving in the crystallizer 25 to 30% of a finished batch to act as seed for the... 

A major interest in using this new process [8] is the value of the temperature at which seeding can be done with the cocoa butter particles supercritically generated. At 305 K the chocolate is less viscous, this is advantageous in term of flowability and energy consumption. An additional advantage lies in the fact that the time needed to obtain a well-tempered chocolate is shorter (about 5 min). Moreover, the overall quantity of seeds to temper the chocolate is very small. Therefore, a scaling-up of this process to an industrial scale appears feasible. 

Jensen, G.H. and Korschgen, L.J. (1947) Contents of crops, gizzards, and droppings of bobwhite quail force-fed known kinds and quantities of seeds. Journal of Wildlife Management 11, 37-43. 

Kovac, V., Alonso, E., Revilla, E. (1995). The effect of adding supplementary quantities of seeds during fermentation on the phenolic composition of wines. Am. J. Enol. Vitic., 46, 363-367. 

These treaters are designed to apply a small amount of pesticide solution to a large quantity of seeds. The pesticides suitable for this treatment are moderately volatile liquids which need not cover each seed entirely to achieve good... 

The critical nature of these interactions is the key factor in causing difficulty in scale-up of nucleation-based crystallization processes—even with small quantities of seed. 

If growth-dominated crystallization is desired, with the presence of a sufficient quantity of seed and a sufficiently slow addition rate, the concentration in solution may remain completely in the metastable region as crystallization proceeds. The closer the solution concentration profile is to the equilibrium solubility curve (B-C), the higher the possibility of achieving an all-growth process. 

One impediment to the cultivation of jatropha for the production of bio-fuel is that it would threaten the growing of food crops and the technology of commercial biodiesel production plant is not yet readily available on the market. However, the area of land that would be brought under jatropha cultivation during the initial years would not yield adequate quantities of seeds for a trans-esterification unit to operate economically. Farmers, on the other hand, would not go in for jatropha cultivation on a commercial basis without being assured of a reliable market. Clearly, it is necessary to find alternative uses for the oil in its natural form (i.e., without trans-esterification), for which a large quantity of the oil can be used for soap making. 

In moderate doses, alfalfa is beneficial because of the large quantities of iron and vitamins it contains. However, the seeds contain relatively high levels of the toxic amino acid canavanine, which may promote pancytopenia with routine ingestion of large quantities of seeds. 

In general, in order to obtain a narrow crystal size distribution (CSD), undesired nucleation should be avoided. In batch crystallization, the use of an optimal quantity of seed crystals of an optimal size may be the way to obtain a narrow CSD. According to Kohl et al. [8], the metastable zone of organic compound systems can be quite wide. Therefore, primary crystallization occurs only at a very high level of supersaturation. 

One use of the law is demonstrated by the following example. If a quantity of seed crystals of known CSD is added to a crystallizer, it is possible to estimate the CSD of the final product by the following procedure. 

In the spring of 1942, Dr. Stevenson supplied a few federal experimental farms and stations with the small quantity of seed he had on hand. The harvest of that year amounted to 2600 pounds (52 bushels) of seed of Brassi-ca napus species. A considerably larger quantity of seed than this was required for planting in 1943 to relieve the serious shortage of rapeseed oil. Dr. Stevenson located and purchased a total of 41,000 pounds from U.S. seed companies. This seed had originally been secured from Argentina and the name Argentine for the Brassica napus was widely used in the early years of production, and still is applied to the varieties of the Brassica napus species. 

In 1942, the Wartime Agricultural Supply Board instructed the Forage Crop Division at Saskatoon to initiate production of rapeseed. Because only a small quantity of seed was available in Canada, 41,000 pounds of seed were purchased from the United States. This seed, which had originated in Argentina, became the source of Canadian varieties of Brassica napus and rapeseed of the Brassica napus species came to be known as Argentine rape in Canada (rape in Europe). 

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